Electrostatic coating apparatus



July 27, 1954 M. RANSBURG I 2,684,656

ELECTROSTATIC COATING APPARATUS Filed July 30, 1949 4 Sheets-Sheet lINVENTOR.

EDWIN M. RAN SB URG ATTORNEY July 27, 1954 E, M. RANSBURG 2,534,656

ELECTROSTATIC COATING APPARATUS 4 Sheets-Sheet 2 Filed July 30, 1949INVENTOR. EDWIN M. RANSBURG ATTORNEY July 27, 1954 E, M. RANSBURG2,684,656

ELECTROSTATIC COATING APPARATUS Filed July so, 1949 4 Sheets-Sheet sINVENTOR.

E DWIN M. RANSBURG ATTORNEY July 27, 1954 E. M. RANSBURG ,684,656

ELECTROSTATIC COATING APPARATUS Filed July 50, 1949 4 Sheets-Sheet 4INVENTOR.

EDWIN M. RANSBURG ATTORNE Y Patented July 27, 1954 ELECTROSTATIC COATINGAPPARATUS Edwin M. Ransburg, Indianapolis, Ind., assignor to HamburgElectro-Coating Corp., Indianapolis, Ind., a corporation of IndianaApplication July 30, 1949, Serial No. 107,687

12 Claims.

This invention relates to electrostatic coating and more particularly toimproved coating apparatus in which liquid coating material is bothelectrostatically atomized and electrostatically deposited upon anarticle to be coated.

This application is a continuation in part of the co-pending applicationof Edwin M. Ransburgjserial No. 57,260, filed October 29, 1948.

In apparatus employed for electrostatically atomizing andelectrostatically applying liquid coating material to discrete articlesor sheet material, it is known to move the articles or sheet materialthrough a coating zone in which the coating material is applied to themby an electrostatic atomizing head. In some of these prior applicationsthe atomizing head comprised an elongated discharge member having anatomizing surface or surfaces to which the coating material was fedthrough a series of restricted orifices. In other atomizing heads of theprior art which have been provided with elongated dis charge members,the coating material was fed to the surface of such members by means ofan elongated orifice with an extended opening substantially of the sameextent as a discharge result that'the spray pattern produced is not ofuniform density throughout its extent. Even when the coating material isdistributed uniformly along the discharge member it sometimes happensthat the atomized material leaves the member in more or less discretestreams or jets and hence tends to be deposited in a striped pattern.

It is an object of this invention to overcome the disadvantagesheretofore attendant upon the electrostatic atomization of coatingmaterial from an elongated atomizing head. Another object of thisinvention is to arrange in a novel Way an electrostatic atomizing headwhereby an improved, uniform coating on articles and a sheet material isobtained. A further object of this invention is to arrange a pluralityof electrostatic atomizing heads along a path of articlemovement forcoating the articles moved over the article-path. A still further objectof this invention is to provide novel apparatus so constructed and sodisposed relative to the horizontal that any tendency of the material tobe deposited in stripes is eliminated. Still another object of thisinvention is to provide an apparatus having the above characteristicswhich will be simple in construction and durable in use and which can bereadily inspected, serviced and repaired in the field. Other objects andfeatures of the invention will be apparent from the specifications andclaims.

In the accompanying drawing Fig. 1 is a fragmental isometric viewillustrating a coating apparatus; Fig. 2 is a fragmental rear elevationof the apparatus shown in Fig. 1; Fig. 3 is a View taken along line 3-3of Fig. 1 with the article and its support shown in both a tilted anduntilted position; Fig. 4 is a View taken along line 4-6 of Fig. 1;Figs. 5 and 8 are fragmental, isometric views illustrating otherembodiments of my invention; Fig. 7 is an orthographic view of thearticle and discharge member shown in Fig. 6 with a section through thedischarge member to aid in showing the form of discharge member and itsedge; Fig. 8 is a circuit diagram illustrating a circuit which isadapted to control the apparatus shown in Fig. 6; and Fig. 9 is a Viewlike Fig. 4 of a modified form of the invention.

In Fig. 1 I have illustrated an arrangement of apparatus suitable forcoating articles II! which are illustrated as acoustic pans which arerectangular metal panels provided with narrow peripheral flanges. Suchapparatus embodies a conveyor which includes chain I I in engagementwith sprockets I2, only one of which is shown. The conveyor may bedriven in the direction indicated by the arrows (Figs. 1 and 2 byconnecting to one of the sprockets I2 a motor with suitable speedreducing means or other suitable driving means. A plurality of articlesupports I3 are connected to the chain I I for carrying the articles Itin succession along a predetermined path as illustrated in Fig. 1. Eacharticle support I3 comprises a vertical rod I4 and horizontal cross barsI5. A cam member I! (Figs. 2 and 3) is disposed along the conveyor andis adapted to engage the horizontal bars I5 of the article supports I 3to tilt the article supports and the articles at an angle to thehorizontal just prior to their moving past the atomizing apparatus(which will be described hereafter) and to maintain them tilted untilthey are moved past the atomizing apparatus.

Disposed above the articles near the forward end of the conveyor is apreheat unit 26 for heating the articles prior to their passing past theelectrostatic atomizing apparatus. This preheat unit is not essential tothe invention and may be used. to dry articles which have just beencleaned or to improve the initial setting or" the coating materialapplied to the articles.

Farther along the conveyor there is disposed above it an electrostaticatomizing device 2! from which liquid coating material iselectrostatically atomized and electrostatically deposited on thearticles. To effect electrostatic atomization of the coating materialand electrostatic deposition thereof on the articles iii, anelectrostatic field of appropriate strength is maintained between thedevice 2! and the ar ticles. For this purpose the articles may begrounded through the conveyor while the device 2! is insulated fromground and connected to one terminal of a high voltage source 22, theother terminal of which is grounded.

The electrostatic atomizing device 21, which is" also shown in Figs. 3and 4, comprises structural members 23 which may be supported in anysuitable manner. Mounted on the structural members 23 are two elongateddischarge members 24 and 25 which are shown as shaped in cross sectionto present toward the articles l relatively sharp edges 25 and 2'!respectively. The dis charge members are arranged on the structuralmembers 255 so that upwardly presented surfaces 28 and 2e are slopeddownwardly toward the edges is and 27 and these edges are themselvesinclined at an angle to the horizontal along their longitudinal extent.Also, transverse to their elongation the members 24 and 25 are arrangedat an angle to the vertical with their edges 26 and 2'? directed towardeach other. An average potential gradient of the order of 10,000 voltsper inch is maintained between the members 24 and 25 and the articlesIii moving past them, and as a result an electrical dischage will existalong the edges 26 and 2'! and an electrostatic field will exist betweenthe members 24' and 25 and the articles is so that liquid coatingmaterial fed to the edges 26 and 2? will be electrostatically atomizedand electrostatically deposited onto the articles Hi, as more fully setforth and described in my co-pending application above referred to.

The coating material distributing means which supplies liquid coatingmaterial to the surfaces 28 and 29 of members 2d and 25 and which isshown in Figs. 1 and 4, comprises a reciprocator 36 arranged toreciprocate parallel to discharge members 24 and 25 a supportingstructure 3| carrying liquid dispensing devices 35 and 36.

The upper end of each dispenser is adapted to be connected to a flexiblehose 34 by which liquid coating may be supplied to each dispenser eitherby gravity or by positively produced pressure. The lower ends ofdispensers 35 and 36 are provided with nozzles 31 and as which arepositioned adjacent discharge members 24' and 25 and are spacedtherefrom as shown in Figs. 1 and 4 to direct streams of coatingmaterial onto surfaces 28 and 29 rearwardly of edges 25 and 21. Whilethe nozzles 31? and 38 are shown as being spaced from the dischargemembers 24 and 25, the in-- vention is not limited to this arrangement,as nozzles arranged in sliding engagement with corresponding dischargemembers would operate satisfactorily. While the detailed construction ofthe reciprocator is not shown in Figs. 1, 3 and 4, it may be of the typeshown in Fig. 6 which will be described hereafter or any other suitablereciprocator well known in the finishing industry.

Disposed along the conveyor beyond the electrostatic atomizing device2!, there is shown a drying oven 39 which may be used when it is desiredto accelerate drying of the coated articles is prior to their removalfrom the conveyor. F

It is understood, however, that the drying oven is not an essential partof my invention.

In operation of the apparatus shown in Figs. 1-4 inclusive, articles I0are placed on supports l3 and moved by the conveyor past the preheatunit which serves to thoroughly dry the articles and preheat them, wheresuch treatment is necessary, to accelerate the setting of the liquidcoating material applied by the electrostatic atomizing device 2|. Afterpassing the preheat unit 20 the articles are tilted so that the majorsurface to be coated is generally parallel to the edges 26 and 21. Whilethe articles are in this tilted position they are moved past theelectrostatic atomizing device 2|.

The coating material supplied to the reciproeating dispensers 35 and 35is distributed along the longitudinal extent of surfaces 28 and 29rearwardly of the discharge edges 26 and 21 from where the coatingmaterial flows to these edges under the influence of gravity and iselectrostatically atomized therefrom and electrostatically deposited onthe articles Hi passing the edges 26 and 21 by the eelctrostatic fieldwhich exists between these edges and the articles. The rate at whichcoating material is supplied to the nozzles 31 and 38 is controlled soas to insure that the discharge members 24 and will not receive morecoating material than can be atomiz'ed from their discharge edges. Therate of reciprocation of the structure 31 and the dispensers and 3B isadjusted as necessary to maintain a supply of coating material forelectrostatic atomization along the desired extent of the edges 26 and21.

It is to be noted that the articles to be coated need not be electricalconductors. When articles made of highly effective insulating materialsuch as glass are being coated, it is desirable that the surface to becoated be backed by a grounded, electrical conductor. However, if thearticles are of poor insulating material, such as wood, no conductivebacking is necessary.

Generally speaking, it is advisable that the length of the dischargeedges 26 and 2? be longer than the parallel dimension of the surface orsurfaces opposed to them and that coating material be distributed to aportion of each edge of approximately the same dimension as the paralleldimension of the opposed surface. The dimension of the portion of thedischarge edge to which coating material is distributed, however, may inmany instances depending upon the nature of the article be somewhat lessthan the parallel dimension of the opposed surface of the articlewithout causing undue lack of uniformity on such surface.

Where the article or articles have flanges to be coated or similarsurfaces such as the flanges of article l0, special consideration shouldbe given to the distribution of coating material on each dischargemember and to the location and orientation of the discharge members withrespect to the articles and the flanges. To aid in the coating of theside flanges (those parallel to the direction of article movement) itwill be advisable to distribute coating material to a longer portion ofthe edges 26 and 27 than would be required if only the top surface ofarticles H] were to receive a satisfactory coating. To aid in coatingthe two transverse flanges of the articles l9 (those normal to thedirection of article movement), it will be advisable to orient one ofthe discharge members at an angle so that its discharge edge isgenerally parallel to one of the transverse flanges and coating materialdistributing surface is sloped downwardly toward the discharge edge andtoward one of the transverse flanges in such a manner that an extensionof the coating material distributing surface will intersect thetransverse flange at least during a portion of the travel of the articlethrough the coating zone.

' The second discharge member should be tilted in the manner describedto improve the coating on the other transverse flange. Fulfilling theseconditions for the articles shown, these discharge members may thus beoriented so that their coating material distributing surfaces are slopeddownwardly toward each other as shown in Fig. 1 or they may be orientedso that their coating material distributing surfaces are slopeddownwardly in opposed directions as shown in Fig. 9. As the parts ofFig. 9 are the same as those described with reference to Fig. 4 (withthe exception of the slope of the material distributing surfaces justmentioned), similar parts have been given similar, but primed, referencenumerals, and further detailed description is believed unnecessary.

Coating material electrostatically atomized from an extended dischargeedge, such as the edge of either of the members 24 and 25, (or 24 and25) tends to leave such edge in the form of more or less well definedstreams spaced from each other along the edge. I have discovered that byarranging the discharge edge at an angle to the horizontal when theelectrostatic coating apparatus is in operation, these separate streamsof coating material progress continuously toward the lower end of theedge as a result of gravity. The action resulting from the inclinedpositioning of the discharge member eliminates the striping tendencywhich would otherwise exist and aids in obtaining a coating of improveduniformity. I have found that for most liquid coating materials ablade-inclination in the neighborhood of 20 degrees to 25 degrees willbe sufficient to eliminate the striping tendency. With relativelyviscous materials, greater inclinations may be needed; but ordinarilylittle if any benefit is to be derived from inclinations greater than 60degrees.

Since the inclined positioning of the discharge member causes liquidcoating material deposited on its upwardly presented surface to movedownwardly longitudinally of its extent prior to its reaching thedischarge edge, the movement of the liquid distributing nozzle should beadjusted so that its path is displaced slightly upwardly andlongitudinally along the discharge member relative to the desired extentof the spray pattern issuing from the discharge edge.

The slope of the surfaces 28 and 29 transversely of the respective edges26 and 21 causes the material to flow to these edges by gravity from thepoints at which it is deposited on the sloping surfaces. As a result, itis possible to dispose the nozzles 31 and 38 well back from the edges 26and 21 where they will be electrostatically shielded by the members 24and 25. The members 24 and 25 are conveniently formed entirely ofgoodconducting material, such as metal, in which case the film ofcoating material from the edge where atomization occurs will be indirect contact with the conducting material and connected therethroughto the high-voltage source. Such a direct connection is not absolutelyessential, as it is necessary only that the edge of the film be locatedin a region where the local potential gradient is great enough to efiectatomization and that a field exists for urging the atomized materialtoward the article for deposition'thereon.

The two members 24 and 25 should be located far enough apart so that thepresence of one does not objectionably reduce the strength of the fieldat the edge (26 or 21) of the other. If the distance between the edges25 and 21 is equal to or greater than their distance from the articles,no such objectionable mutual shielding will exist. Besides the advantagepreviously mentioned, the use of more than one discharge member permitsthe application of heavier coatings than could be obtained from a singlemember. a certain amount of spacing between discharge members isdesirable, a single means may be utilized for reciprocating both of thecoating material supplying nozzles associated with each dischargemember,

In Fig. 5 I have illustrated an arrangement of apparatus which issuitable for coating sheet material 40. Such apparatus embodies aconveying means which includes the rollers 4| and 42 which guide thesheet material over a predetermined path through a coating zone.Disposed at one side of the path of sheet-movement through the coatingzone is an atomizing device 44 from which liquid coating material iselectrostatically atomized. To effect electrostatic atomization of thecoating material and electrostatic deposition of the atomized materialon the sheet 40 as it passes the device 44, an electro static field ofappropriate strength is maintained between the device 44 and the sheetmaterial 40. For this purpose the sheet material may be grounded throughthe roller 4! while the device 44 is insulated from ground and connectedto one terminal of a high voltage source 46, the other terminal of whichis grounded.

The atomizing device 44 includes vertical insulating posts 48 and 49which sup-port a beam 50. The beam 50 supports housing 5| which ispivotally connected thereto as shown. The housing 5| may be held atvarious positions relative to the horizontal by an adjustable strut 52which is connected to the beam 50 as shown.

At one side of the housing 5| there is supported in any convenientmanner an elongated discharge member 54 which is preferably ofelectrically conducting material and connected to the ungroundedterminal of the high voltage source 45. The member 54 is shown as shapedin cross section to present toward the sheet 40' a relatively sharp edge55. It also is provided with an upwardly presented surface 56 which maybe sloped downwardly toward the edge 55.

An average potential gradient of the order of 10,000 volts per inch ismaintained between the elongated member 54 and the sheet 40 moving pastit, and as a result an electrical discharge will exist along the edge 55and an electrostatic field will exist between the member 54 and thesheet 40 so that liquid coating material fed to the edge 55 will beelectrostatically atomized and electrostatically deposited onto thesheet 40. The liquid coating material is fed to the surface 56 along theedge 55 in the form of a film extending along the edge between more orless definite limits, such film being created and maintained by anysuitable supplying means. One such means may comprise a carriage 51mounted for reciprocation along slot 58 which extends longitudinally ofhousing 5|. This carriage may bear at its outer end a short length oftube or Even though pipe 59 disposed transversely of the slot 58. Oneend of the tube 59 is connected through a flexible hose 60 with a sourceof liquid coating material which is adapted to be fed to the tube 59 bygravity or by positively produced pressure. To the opposite end of thetube 59 there is connected a nozzle 6| having its outer end disposedrearwardly of the edge 55 so as to be electrically shielded by thedischarge member 55 while discharging coating material onto the surface56. The surface 56 between the edge 55 and the path of nozzle BI issloped downwardly sufiiciently so that gravity will cause the coatingmaterial to flow to the edge 55,

Means which may be employed for reciprocating the carriage 51 and thenozzle 6| may take any form, such as that shown and described in myco-pending application, previously referred to, or that shown in Fig. 6of the drawings and described hereinafter.

The operation of the apparatus just described is similar to theoperation of the apparatus shown in Fig. 1 except that the surface beingcoated is moved in a vertical rather than a horizontal direction.

As previously stated the housing is pivotally connected to the beam 50at one end thereof. This permits positioning the discharge edge 55 atany convenient angle relative to the horizontal. This angle may bevaried depending upon the viscosity of the liquid coating material toeffect the desired gravity induced stream movement referred to above.

Referring to Fig. 6, I have illustrated still another form of coatingapparatus which is adapted for coating articles such as the illustratedcylindrical object 70. Such apparatus embodies a conveyor 'II which isprovided with a plurality of longitudinally spaced spindles I2. Eachspindle I2 has afiixed thereto a pulley I3 which is adapted to engage abelt 14. The belt 14 is adapted to be driven in any convenient manner inthe direction of the arrow placed adjacent the belt for rotating thespindle I2 and the article mounted thereon. The conveyor H may haveassociated with it a switch I6 normally biased to a closed positionprovided with a lever 17 arranged in the manner shown to intermittentlystop the conveyor and bring the articles I0 successively to restopposite the atomizing device 80 now to be described. The circuit inwhich the switch I6 is incorporated is shown in Fig. 8 and will bedescribed in greater detail hereafter.

The atomizing device 80, from which liquid coating material iselectrostatically atomized, is disposed at one side of the conveyor II.To effect electrostatic atomization of coating material andelectrostatic deposition thereof on the article 18, an electrostaticfield of appropriate strength is maintained between the device 80 andthe article 78. For this purpose the article I0 may be ground throughthe conveyor II as shown and the device 80 insulated from ground andconnected to the ungrounded terminal of a high voltage source in themanner shown in Figs. 1 and 5.

The atomizing device 80 comprises frame 8! which is mounted onvertically reciprocable rod 82. A reciprocating device 83 is connectedto rod 82 for moving it and the frame 8I vertically between suitable,predetermined limits. The reciprocating device 83 may be of the typedescribed in my co-pending application previously referred to or of anyother suitable type. A bracket 85 is affixed to the rod 82 forsupporting 8' an element 86 which is adapted to operate switches 81 and88 which are biased to a normally open position and are included in thecontrol circuit illustrated in Fig. 8.

On the side of the frame 8| nearest the article I0 and along an inclinedportion thereof, there is provided an elongated discharge member 89which may be of conducting material and which has an upwardly presentedsurface 90 sloped downwardly toward a sharp discharge edge 9I. Themember 89 is formed so that the edge 9| follows a helically inclinedpath which generally follows and is spaced from the cylindrical surfaceof the article 10, as is clearly illustrated in Fig. '7. The member 89also is provided with a cam surface 92 whose function will be describedhereafter.

An average potential gradient of the order of 10,000 volts per inch ismaintained between the discharge member 89 and the article 10 spacedfrom it, and as a result an electrical discharge will exist along thedischarge edge 9| and an electrostatic field will exist between themember 89 and the article I9 so that liquid coating material fed to theedge 9| will be electrostatically atomized and electrostaticallydeposited on the surface of the article 18. The liquid coating materialfed to the surface 90 forms a film supported on such surface extendingalong the edge BI between more or less definite limits. Although thefilm can be created and maintained by any suitable supplying means, thecoatin material supplying means shown comprises a pipe 93 which isbiased forwardly by a compression spring 94 mounted on the pipe 93between a shoulder formed thereon and a sleeve H2. One end of the pipe93 is connected as through a flexible hose 95 with a source of coatingmaterial which is adapted to be fed to the pipe 93 either by gravity orby positively produced pressure. The supply of the coating material maybe turned on and off by an air-controlled valve 98. The compressed airis supplied to valve 98 through pipe 99 and is controlled by valve III.To the opposite end of the pipe 93 there is connected nozzle 96 havingits outer end disposed rearwardly from edge 9| so as to be electricallyshielded thereby. A cam follower 91 is affixed to the pipe 93- and isadapted to engage the cam surface 92 of the member 89 to guide thenozzle 96 in its path of movement rearwardly of the discharge edge 9|and over the surface 90. The cam follower 91 is held in engagement withthe cam surface 92 by the spring 94.

The means employed to reciprocate the pipe 93 and the nozzle 96 may takevarious forms. In Fig. 6 such means is shown as comprising a cylindricalcam I09 with threads WI and I02 which is rotatably mounted in bracketsI83 and I04 on frame 8|. The cam I08 is adapted to be driven by airmotor I05 which may be connected to a source of compressed air throughflexible hose [06, in which there is provided the valve III. A carriageI08, which is movably mounted on rails I09 and I I8 and which includes akey (not shown) adapted to follow threads IOI or I02, is reciprocatedalong such rails by the cam I00 in known manner. The sleeve I12 ispivotally mounted intermediate its ends on pins H3 which are supportedon the carriage I08, and pipe 93 is slidably mounted within the sleeveH2. A spring plate H5 mounted on the carriage I08 is adapted to engagethe forward end of sleeve H2 so as to bias the nozzle 96 into continualengagement with the surface 90 of the .discharge'member 89. The threadsIOI and I02 in cam I are of variable pitch to vary the speed ofthecarriage I08 so that the nozzle 96 moves along the helical dischargeedge 9| with a generally uniform rate of speed. If it is desired to movecarriage I08 at a uniform speed, the threads I6I and I02 in cam I00should be of constant pitch.

The control circuit for controlling the operation of the apparatus shownin Fig. 6 is shown in Fig. 8 and includes switches 16, 81 and 88previously described and relays I22, I23 and I24. The control circuitalso includes a manual bypass switch I46 which is connected toconductors I50 and II leading to the high voltage source forindependently controlling the high voltage source and manual by-passswitch I41 connected in the circuit including solenoid I forindependently controlling the air valve III. Relay I22 comprises coilI26 and contacts I21, I28, I29, I and I3I. Relay I23 comprises coil I33and contacts I34, I and I36. Relay I24 comprises coil I38 and contactsI39, I40, I4I, I42, I43 and I 44.

As shown in Fig. 8 the control circuit is in the condition when theconveyor H is moving and the electrostatic coating device 80 isinoperative. Under this condition the relay I22 is energized andholding-circuit contact I21 and conveyormotor contacts I28, I29 and I30are closed and contact I3I is open. Contact I3I controls ('1) a circuitwhich includes coil I33 of relay I23, (2) circuits which includesolenoids H1 and I I8, and (3) a circuit which includes coil I38 of therelay I24. The circuit by which coil I26 of relay I22 is maintained inan energized condition and which is referred to as a holding circuitconsists of conductors I52, I53, contact I21, conductor I54, switch 16,conductors I55 and I56, coil I26 and conductors I5I and I58.

When one of the spindles 12 on the conveyor 1I engages lever 11 ofswitch 16, this switch is temporarily opened and coil I26 of relay I22is de-energized opening holding circuit contact I21 and conveyor motorcontacts I28, I29 and I30, and closing contact I3 I. This stops theconveyor motor. The closing of contact I3I energizes the circuit whichincludes solenoid I I8 which actuates the valve I I 9 to initiate theupward movement of the reciprocator 83-. v This circuit consists ofconductors I52, I60, contact I3I, conductors I6I, I62, I63, switch 88,conductors I64, I65 and I66, contact I36 (which is closed when relay I23is deenergized) conductor I61, coil H8 and conductors I68, I69, I10, HIand I58. The closing of contact I3I also energizes the circuit whichcontrols relay I24. This circuit consists of the same portion of theprevious circuit from conductor I52 to junction I12 and therefrom itconsists of conductor I13, contact I 44, conductors I14 and I 15, coilI38 and conductors I16, HI and I58. Upon the energization of coil I38through the circuit just described contact I44 opens and thereafter coilI38 is energized through the circuit which consists of conductors I52,I60, contact I 3I, conductors I6I, I62, I18, contact I39, conductorsI19, I15, coil I38, conductors I16, HI and I58. Upon the energization ofcoil I38 contacts I43, I42, MI and I 40 are closed in addition tocontact I44 being opened and contact I 39 being closed. Closing contactsI42 and I43 closes a circuit which energizes the high voltage source.This circuit consists of conductors I8I, I82, contact I43, conductorsI83, I50, I5I, I84, contact I42, conductors I85 and I86. When contacts I40 and I are closed 10 a current source is connected to the solenoid I20which controls the air valve-I I I. This is done by means of a circuitwhich consists of conductors I88, I89, contact I4I, conductors I90 andI3I, coil I20, conductors I92, I93, contact I48 and conductors I94 andI95.

Switch 88 is opened upon the initiation of the upward movement of therod 82 of air reciprocator 83. After the air reciprocator moves theatomizing device upward a predetermined distance, it actuates switch 81by means of element 86 and momentarily closes switch 81. This energizescoil II1 through the circuit which consists of conductors I52, I60,contact I3I, conductors I6l, I91, I98, switch 81, conductors I99 and200, coil II1, conductors 20I, I69, I10, HI and I58. The energization ofcoil II1 actuates valve II9 which reverses the movement of the rod 82 ofthe reciprocator 83 to a downward direction. Closing switch 81 alsoenergizes coil I33 of relay I28 through the circuit which consists ofconductors I52, I60, contact I3I, conductors I6I, I91, I98, switch 81,conductors I99, 203, 204, coil I33, conductors 205, I10, Ill and I58.Upon the energization of coil I33 contacts I34 and I35 are closed andcontact I36 is opened. After the switch 81 again opens after itsmomentary closing, the coil I33 remains energized through the circuitwhich includes contact I34. This circuit consists of conductors I52,I60, contact I3I, conductors I6I, I91, 201, contact I84, conductors 288,204, coil I33, conductors 205, I10, HI and I58.

When the element 86 reaches and engages the switch 88 on the downwardmovement of the rod 82 of the reciprocator 83, switch 88 is closed. Thismomentarily energizes coil I26 of relay I22 through the circuit whichconsists of conductors I52, I50, contact I3I, conductors I6I, I62, I63,switch 88, conductors I64, I65, 2I0, contact I35, conductors 2II, I56,coil I26 and conductors I51 and I58. After coil I26 is energized holdingcircuit contact I21 and conveyor motor contacts I28, I29 and I30 areclosed and contact I3I is opened. Upon the closing of contact I21, coilM6 is energized through the circuit previously described. The closing ofconveyor motor contacts I28, I29 and I30starts the conveyor motor. Theopening of contact I3I at the same time deenergizes relay I23 and I24and the circuits including the solenoids H1 and 'I I8. This makessolenoids II1, I I8 and I20 and the high voltage source inoperative. Afeature essential to the operation of the circuit just described is thatthe switch 88 be held closed when the reciprocator 83 comes to rest atthe bottom of its stroke.

In the operation of the apparatus of Figs. 6 and 8, the connectionsestablished as shown in Fig. 8 cause the conveyor to move including thespindles 12 in the direction of the conveyor arrow shown in Fig. 6.During movement of the conveyor, the rod 82 is at the bottom of itsstroke, thus maintaining switch 88 closed through element 86. When oneof the spindles 12 engages lever 11 of switch 16, this switch ismomentarily opened to break the holding circuit of relay I22 whereby theconveyor motor is stopped and the spindle which has actuated switch 16is stopped adjacent the electrostatic atomizing device 80 in theposition shown in Fig. 6. The de-energization of relay I22 also closescontact I3I which permits energization of solenoid I I8 to start theoperation of the reciprocator 83 for causing upward movement of theatomizing device. The closing of contact I3I also permits energizationof relay I24 which permits the energization of the high voltage sourcewhich creates an electrostatic field between the discharge member 89 andthe article Hi and also permits energization of solenoid I21": whichopens air valve l H for supplying coating material to the nozzle 98 andenergizes the air motor Hi5. While air motor I reciprocate the carriageHi8, the spring 94, acting between the sleeve I I2 and a shoulder on thepipe 93, holds the cam-follower 9'! against the cam 92, which is soshaped that the nozzle 96 moves parallel to the edge 9| as it dischargescoating material onto the surface 99. Coating material discharged fromnozzle 95 flows down the radial slope of the surface 98 to the edge 9|.As atomizing device 86 is moved upwardly theelectrostatic field betweenit and the article H3 electrostatically atomizes the coating materialand electrostatically deposits it on the article '59. When'the atomizingdevice 80 has moved upwardly its predetermined distance, the element 86actuates switch 81 to de-energize solenoid H8 and to energize solenoidH1 which actuates valve H9 and reverses the movement of the atomizingdevice 80 to a downward direction. During the downward movement of theatomizing device 89 the supply of coating material is continued'to theedge 9i and coating of the article iii i continued during the downwardmovement of the atomizing device 80. After the atomizing device has madeits predetermined downward movement, the element 86 closes switch 38whereby relay I22 is energized and relays I23 and I2 3 ared-e-energized. This de-energizes the high voltage source, cuts off thesupply of coating material to the nozzle 55 and stops the reciprocationof the nozzle 96 and the atomizing device 80. Also, upon there-energization of relay I22 the conveyor motor is started to move thearticle that has just been coated along the conveyor and to permitanother article to move into coating position relative to the atomizingdevice.

It is evident that valve means could be provided which would permitshutting off the supply of coating material during any part of thereciprocating cycle of the atomizing device all. The helical inclinationof the edge 9! in Fig. 6 and the longitudinal inclination of the edge 55in Fig. 5 function to eliminate striping tendencies in the same manneras does the inclination of the edges 2-6 and 2? in Figs. 1 to 4. Thestate ments made above, in connection with the apparatus of Figs. 1 to4, relative to the conducting character of the members 24 and 25, applyequally well to the discharge member 54 of Fig. 5 and discharge member89 of Fig. 6. Also applicable to the arrangements shown in Figs. 5 and 6are the statements previously made relative to the necessity of a.backing electrode if the article being coated is made of highlyeffective insulating material.

I claim as my invention:

1. In an electrostatic atomizing system for use in the electrostaticdeposition of liquid coating material on an article, a support for thearticle to be coated, a discharge member having an extended, dischargeedge, a support for supporting said member in a position with said edgespaced from an article on said support and inclined at an angle to thehorizontal of between and 60 degrees, and means for distributing liquidcoating material to said member along said edge for atomizationtherefrom, the spacinggbetween said edge and the article beingsufficient to permit substantial dispersion of the particles 12 underthe influence of electrostatic forces dur-' ing their movement towardthe article.

2. In an electrostatic atomizing device for use in electrostaticdeposition of liquid coating material, a plurality of discharge members,each of said members having a generally upwardly presented surfaceterminating at an extended, discharge edge, means for supporting saidmembers in spaced relation to each other and for maintaining said edgesin substantially inclined positions and generally parallel to each otherand with, each of said associated surfaces sloping downwardly towardsaid edges, and a liquid dispensing means associated with each of saidmembers for supplying liquid coating material to each of said upwardlypresented surfaces.

3. In an electrostatic atomizing device for use in electrostaticdeposition of liquid coating material, a pair of discharge members, eachof said members having a generally upwardly presented surfaceterminating at an extended, discharge edge, means for supporting saidmembers in spaced relation to each other and with their upwardlypresented surfaces sloping downwardly toward their respective dischargeedges and toward each other, and a liquid dispensing means associatedwith each of said members for supplying liquid coating material to eachof said upwardly presented surfaces.

l. The invention set forth in claim 2 wherein adjacent ones of saidmembers are sup-ported with their upwardly presented surfaces slopingdownwardly and away from each other.

5. Electrostatic coating apparatus having, in combination, a dischargemember having a generally upwardly presented surface terminating at anextended discharge edge, means for supporting said member with said edgeinclined to the horizontal and with said surface sloping downwardlytoward said edge, a conveyor, a plurality of article supports on saidconveyor for carrying articles successively past said edge in spacedrelation thereto, means for adjusting each of said article supportsprior to their movement past said edge for presenting the surfaces ofthe articles to be coated in a plane generally parallel to said edge,means for supplying liquid coating material to said member surface, andmeans including a high voltage source for creating between the articleson said article-supports and coating material on said edge anelectrostatic field for electrostatically atomizing the coating materialand electrostatically precipitating it onto the articles.

6. In electrostatic coating apparatus, means for conveying an articlealong a predetermined path, a plurality of discharge members spacedalong said path, each of said members having an extended, discharge edgepresented laterally of said predetermined path and toward and in spacedrelation to an article on said conveying means, a liquid dispensingmeans associated with each of said members for distributing liquidcoating material at a controlled rate to each of said members foreffecting a uniform distribution thereof along each of said edges tomaintain on said edges liquid coating material for atomization from aplurality of spaced points therealong, and means including a highvoltage source for creating between an article on said conveying meansand coating material on the edges of said discharge members anelectrostatic field capable of electrostatically atomizing such coatingmaterial and electrostatically dispersing and precipitating it onto thearticle, said article conveying means and said discharge members beingso relatively disposed that the distance between the article surface andsaid edges will be materially greater than the distance between adjacentones of the points at which atomization takes place, whereby theatomized particles during their movement to the article by the action ofthe field will be widely dispersed.

7. The invention set forth in claim 6 with the addition that each ofsaid discharge members includes a generally upwardly presented surfacesloped downwardly toward and terminating at said edge and said edgebeing substantially inclined at an angle to the horizontal of between 26and 60 degrees relative to its extent.

8. The invention set forth in claim 6 with the addition that said liquiddistributing means comprises a nozzle and means for reciprocating saidnozzle along said edge and spaced therefrom.

9. In an electrostatic coating system for use in the electrostaticdeposition of liquid coating material on an article, a support for thearticle to be coated, a plurality of discharge members, each of saidmembers having a surface terminating in an extended discharge edge,means for supporting said members in spaced relation to each other andwith the edge of each of the members spaced from an article on saidsupport, liquid dispensing means associated with each of said membersfor supplying liquid coating material to each of said surfaces for flowto said edges, means for creating an electrostatic field of highpotential between an article on said support and the coating material ateach of said edges capable of electrostatically atomizing and dispersingsuch coating material and electrostatically precipitating it onto thearticle, the spacing between each of said edges and the article beingsufiicient to permit substantial dispersion of the particles duringtheir movement toward the article under the influence of said field.

10. In an electrostatic atomizing system for use in electrostaticdeposition of liquid coating material on an article, a support for thearticle to be coated, a discharge member having a generally upwardlypresented surface terminating at an extended edge, means for supportingsaid member with said edge inclined to the horizontal and with saidsurface sloping downwardly toward the edge, means for adjusting saidsupporting means for changing the angle of inclination of said edge, andmeans for supplying liquid coating material to said member-surface foratomization from a plurality of streams spaced along said edge, saidedge being inclined to the horizontal at an angle of not more than 60but sufiicient to cause the 14 streams of coating material to progresscontinuously toward the lower end of the edge, the spacing between saidedge and the article being sufficient to permit substantial dispersionof the particles under the influence of electrostatic forces duringtheir movement toward the article.

11. An electrostatic atomizing system for use in the electrostaticdeposition of liquid coating material on an article, a support for thearticle to be coated, a discharge member having an extended edge, meansfor supplying liquid coating material to said member and for forming thematerial into a substantially continuous body having a relatively thinterminus extending along said edge, means for creating an electrostaticfield between the terminus of said body and the article capable ofatomizing said material from a plurality of streams spaced along saidterminus, the spacing between said terminus and an article on saidsupport being sufiicient to permit substantial dispersion of theatomized particles by said field during their movement toward thearticle, and means for maintaining said edge inclined to the horizontalat an angle sufficient to cause the streams of coating material, duringsaid atomization, to progress continuously toward the lower end of theedge.

12. In an electrostatic atomizing system for use in the electrostaticdeposition of liquid coating material on an article, a support for thearticle to be coated, a discharge member having an extended edge, meansfor supplying liquid coating material to said member and for forming thematerial into a substantially continuous film along said edge foratomization from a plurality of streams spaced along said edge, thespacing between said edge and an article on said support being sumcientto permit substantial dispersion of the atomized particles under theinfluence of electrostatic forces during their movement toward thearticle, and means for maintaining said edge inclined to the horizontalat an angle sufiicient to cause the streams of coating material, duringsaid atomization, to progress continuously toward the lower end of theedge.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,855,869 Pugh Apr. 26, 1932 2,070,972 Lindenblad Feb. 16,1937 2,224,391 Huebner Dec. 10, 1940 2,247,963 Ransburg et al July 1,1941 2,408,143 Huebner Sept. 24, 1946 2,438,561 Kearsley Mar. 30, 19482,451,288 Huebner Oct. 12, 1948

